1. Field of the Invention
This invention concerns apparatus for improving the fuel economy of an automotive vehicle, and more particularly relates to apparatus which interacts with a conventional cruise control system to provide greater mileage per unit of fuel consumed.
2. Description of the Prior Art
Electronic throttle controllers are well known for operating an engine throttle valve to control the rate of fuel flow to the combustion chamber of an engine. Typically, the throttle controller receives an acceleration input signal from the operator of the vehicle via an accelerator pedal. The farther the pedal is depressed, the more the throttle valve is opened, which permits more fuel to be consumed by the engine and the vehicle to travel faster.
Some throttle controllers can operate automatically as a “cruise control” to maintain the speed of the vehicle at a cruising speed set by the driver. The cruise control provides a convenient means for a driver to maintain vehicle speed without using foot pedals, which can be especially advantageous on long trips. Typically, such conventional cruise controls use an input from a speedometer or engine speed sensor to monitor the cruising speed of the vehicle. Due to varying terrain, friction and wind resistance the speed controller is nearly continuously correcting for deviations from the desired speed. Consequently, the throttle is constantly fluctuating to allow more or less fuel to be consumed by the engine to maintain the set speed.
A problem with such cruise controls is that the continuous throttle adjustments lower the fuel economy of the engine. This is primarily due to the inefficiencies involved with non-constant burning, which include counteracting momentum losses of the moving components of the engine as well as that of the overall vehicle.
Most cruise controls include stored error correction algorithms that define the response time and duration of the throttle adjustments. These algorithms are commonly designed with smoothness, accuracy and responsiveness being the highest priorities. Fuel economy is typically not a factor in the design of the algorithms.
U.S. Pat. No. 5,944,766 discloses a cruise control having control algorithms designed to improve the fuel economy of the vehicle. When it is sensed that the vehicle is gaining momentum, the algorithms instruct the speed controller to override the normal control of the throttle and set back the throttle position to a prescribed percentage (such as 50% or 80%) of its normal position. Thus, fuel consumption is minimized during and after the vehicle travels down hill. As such, the disclosed cruise control has only limited fuel saving benefits.
U.S. Pat. No. 6,213,089 discloses a system for achieving fuel economy by way of delivery of controlled pulses of fuel to a fuel injection mechanism. Although apparently feasible, this system does not easily adapt to interaction with a conventional cruise control system.
Accordingly, there exists a need for a cruise control with improved fuel economizing benefits.
It is therefore a primary object of the present invention to provide control apparatus for improving the fuel efficiency of a conventional cruise control system of an automotive vehicle.
It is a further object of this invention to provide control apparatus as in the foregoing object and operating method amenable to interaction with an existing conventional cruise control system.
It is another object of the present invention to provide control apparatus of the aforesaid nature of rugged, durable construction predisposed to low cost manufacture.
These objects and other objects and advantages of the invention will be apparent from the following description.